Electrohydraulic blowout preventer



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ELECTROHYDRAULIC BLOWOUT PREVENTER Filed April 20, 1962 7 Sheets-Sheet l INVENTORSI J. A. HAEBER K. W. FOSTER THEIR AGENT 1966 J. A. HAEBER ETAL 3,250,336

ELEGTROHYDRAULIC BLOWOUT PREVENTER 7 Sheets-Sheet 2 Filed April 20, 1962 INVENTORSI J. A. HAEBER K. w. FOSTER BY! Him.

THEIR AGENT May 10, 1966 J. A. HAEBER ETAL 3,250,335

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Y W B 1966 J. A. HAEBER ETAL 3,250,336

ELECTROHYDRAULIC BLOWOUT PREVENTER Filed April 20, 1962 7 Sheets-Sheet 4 FIG. 4

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THEIR AGENT y 1966 .1 A. HAEBER ETAL 3,250,336

ELEGTROHYDRAULIC BLOWOUT PREVENTER Filed April 20, 1962 '7 Sheets-Sheet 5 INVENTORSZ J. A. HAEBER K. W. FOSTER HEIR AGENT May 10, 1966 J. A. HAEBER ETAL 3,250,336

ELECTROHYDRAULIC BLOWOUT PREVENTER Filed April 20, 1962 '1 Sheets-Sheet e INVENTORSI J. A. HAEBER K. W. FOSTER BY: 14m

HEIR AGENT y 0, 1966 J. A. HAEBER ETAL 3,250,336

ELECTROHYDRAULIC BLOWOUT PREVENTER Filed April 20, 1962 T Sheets-Sheet 7 POWER SUPPLY ADJUSTABLE CURRENT- CURRENT SENSITIVE I31 RELAY H30 REVERSING POWER SWITCH) SUPPLY l27" l 2 IHVARIABLE -vo| TAsE Mm... CONTROLLER i '1 l 97 I 125 :28 j (124 MAGNETIC/ ClRCUKT 96 CONTACTOR BREAKER 2 RELAY FIG. I0

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A PPLiED VOLTAGE INVENTORS J. A. HAEBER K. W. FOSTER BY .141

HEIR AGENT United States Patent 3,259,336 ELECTROHYDRAULIC BLGWOUT PREVENTER John A. Haeher and Kenneth W. Foster, Houston, Tex., assignors to Shell Oil Company, New York, N.Y., a

corporation of Delaware Filed Apr. 20, 1962, Ser. No. 189,113 4 Claims. (Cl. 175-7) This invention relates to a blowout preventer adapted to be secured to a well casinghead to control the pressure therein The invenion pertains more particularly to a blowout preventer for use in drilling, completing and work-over operations in oil and gas wells at offshore locations wherein the wellhead assembly is positioned at a substantial depth below the surface of a body of water and operations are carried on from a floating platform on the surface of the water. If desired, a blowout preventer in accordance with the present invention may be left on a wellhead assembly while the well is in pro duction.

During various stages of drilling, production or -servic ing of an oil well, there are occasions when the pressure in the well is sufficient to force the contents of the well upwardly out of the Well, whether the contents of the well be oil, drilling mud, completion fluid, or the like. A blowout preventer is therefore provided at the top of the well for sealing oif the well during such intervals. It may be necessary to close one or more blowout preventers and seal off the well while a drill pipe is in the well, while a tubing string is passing through the casinghead, or while the well and/ or casinghead are otherwise empty.

A blowout preventer of the ram type comprises a hollow body member having aligned pipe openings in one pair of opposite walls to provide a pipe passage therethrough, a pair of horizontally slidable rams arranged for movement toward and away from the pipe passage in the preventer body so as to seal the pipe passage when the rams are in the closed position. Each ram carries a resilient sealing member or valve head arranged to engage its cooperating ram in a fluidtight manner. One set of rams when closed together has a hole extending therethrough which is of slightly smaller diameter than the diameter of a drill pipe against which it is adapted to seal in a fluidtight manner. The other pair of rams in the blowout preventer, known as blind rams, have strightedged resilient sealing members adapted to seal against each other when there is no pipe or tubing string extending through the blowout preventer.

The rams in one type of blowout preventer are closed manually by an operator turning hand wheels connected to threaded valve stems which in turn are connected to the rams. Thus, the blowout preventer is closed in the same manner that two valves would be closed that are set at 180 to each other to close one against the other. It is obvious that manually-actuated valves could not be used in drilling underwater wells. Hence, it is a primary object of the present invention to provide a blowout preventer which may be opened or closed remotely, as from a drilling platform or vessel positioned on the surface of the water, or from a remote location in land operations.

Blowout preventers with hydraulically-actuated rams have been used in well drilling operations on land and are presently the most common type used. The use of hydraulically-operated blowout preventers for drilling underwater wells has not proved entirely satisfactory due to the fact that the hydraulic pressure lines may be easily ruptured and the pressure drop in the hydraulic lines due to friction loss reduces the amount of available pressure to be supplied to the rams of the blowout preventer. The pressure drop in the hydraulic lines may be overcome only 3,250,336 Patented May 10, 1966 by using very large diameter hydraulic lines, but these are very heavy and cumbersome to handle in offshore operations where the drilling platform or vessel may be several hundred feet above the wellhead position on the ocean floor.

It is therefore another object of the present invention to provide an electrically-operated blowout preventer which may be operated by a single multi-conductor electric transmission line extending from a drilling platform above the surface of a body of water to the blowout preventer and wellhead apparatus positioned near the ocean floor.

As an emergency control feature, it is a further object of the present invention to provide an electricallyoperated blowout preventer, for land or sea operations, with a hydraulic prime mover which is adapted to override an non-operative electrical prime mover that is normally employed to operate the blowout preventer.

Another object of the present invention is to provide an electrically-operated blowout preventer wherein the closing force of the rams of the preventer may be adjustably controlled from a remote location, as from a drilling platform on the surface of the water.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view taken in longitudinal projection illustrating a floating drilling barge positioned on the surface of the ocean with an underwater wellhead assembly positioned on the ocean floor when well drilling operations are being carried out;

FIGURE 2 is a fragmental view of the ram type blowout preventer of FIGURE 1 taken partly in cross section and partly in phantom showing the sealing face of the upper far ram and the back end of the lower near ram;

FIGURE 3 is a cross-sectional view taken along the line 3-3 of FIGURE 2 showing a segment of pipe positioned between the upper rams of the blowout preventer;

FIGURE 4 is a view taken patrially in cross section of an electric operator adapted with secondary hydraulic over-ride apparatus of the blowout preventer of FIG- URE 1;

FIGURE 5 is a view taken in partial cross section along the line 55 of FIGURE 4;

FIGURES 6, 7, 8 and 9 are isometric views diagrammatically illustrating various arrangements whereby the electric operators with secondary hydraulic over-ride apparatus of the present blowout preventer may be connected to actuate one set of rams thereof;

FIGURE 10 is a diagrammatic view illustrating one type of control circuit for the blowout preventer of the present invention; and,

FIGURE 11 illustrates a typical curve which may be obtained when plotting ram thrust against applied voltage for one form of a blowout preventer.

Referring to FIGURE 1 of the drawing, a drilling platform or barge 11 of any suitable fioatable type is illustrated as floating on the surface of a body of water 12 and being substantially fixedly positioned over a preselected drilling location by suitable barge-positioning means or by being anchored to the ocean floor 13 by suitable anchors (not shown) connected to the anchor lines 14 and 15. Equipment of this type may be used when carrying on well drilling operations in water depths varying from about to 1500 feet or more. The drilling barge is equipped with a suitable derrick 16 as well as other auxiliary equipment needed during the drilling of a well or during work-over operations. The derrick 16 is positioned over a drilling slot or well 18 which ex-' tends vertically through the barge in a conventional manner. When using the equipment of the present invention, the slot of the barge 11 may be either centrally located or extend in from one edge. However, drilling operations may be carried out over the side of the barge or platform without the use of a slot. Additionally, it is to be understood that the equipment of the present invention may also be used when drilling a well from any suitable operational base positioned above the surface of the water, such for example, as from a platform permanently positioned on the ocean floor.

A typical underwater wellhead structure or assembly is illustrated in FIGURE 1 as comprising a base member 21 which is positioned on the ocean floor 13 and is fixedly secured to 'a conductor pipe or a large-diameter well casing 22 which extends down int-o a well, which has been previously drilled, and is preferably cemented or otherwise anchored therein. Thus, the base structure 21 is rigidly secured to the ocean floor in order to support two or more vertically-extending guide columns 23 and 24 adapted to receive and guide therein guide arms 25 and 26, 25a and 26a and 25b and 26b, which are arranged to slide on vertically-extending guide cables 27 and 28. The lower ends of the guide cables 27 and 28 are anchored to the base structure 21 within the guide colums 23 and 24 while extending upwardly through the water to the drilling barge 11 where they are preferably secured to constant tension hoists 31 and 32. It is to be understood that in an emergency a single guide arm on a guide cable extending between the base structure 21 and the drilling vessel 11 may be employed to position a piece of equipment on the wellhead. A two-cable guide system will be described hereinbelow although generally a guide system having at least three guide cables is preferred.

Centrally positioned above the base plate 21 and fixedly secured thereto, or to the conductor pipe 22, is a well casinghead unit 33 which may be provided with a cement circulation or fluid return line 36 which may be selectively closed by a remotely-operated valve (not shown). The guide arms 25 and 26 are illustrated as being connected to a wellhead connector unit 40 which may be hydraulically or electrically actuated to connect to the top of the casinghead 33 in a manner described in copending patent application, Serial No. 105,068, filed April 24, 1961 and now Patent No. 3,163,222. In the above-identified patent application a wellhead connector 40 is provided with a self-contained electro-hydraulic operating unit which is provided with operating power by an electrical transmission line running from the barge 11 to the underwater wellhead assembly; Alternatively, the wellhead connector could be hydraulically operated by means of a pressure fluid line running to the barge 11.

During the drilling, completion and working over of a well, one or more blowout preventers are normally connected coaxially above the wellhead connector 40. In FIGURE 1 a series of four blowout preventers 43, 44, 45 and 45a are illustrated as being fixedly secured together and forming a unitary package with the wellhead connector 40, which package is adapted to be lowered onto the casinghead 33 in any suitable manner. The lower blowout preventers 43 and 44 are of the ram type and may be mounted in a common housing as will be described hereinbelow. Likewise, the upper blowout preventers which are preferably of the radially-contractible cartridge-type packing unit design, are mounted in a common housing, each packer of blowout preventers 45 and 45a being actuated by a self-contained electr c-hydraulic operating unit 46 and 47, respectively. The selfcontained electro-hydraulic operating units 46 and 47 are described in copending patent application, Serial No. 105,068, filed April 24, 1961, are connected by means of hydraulic conduits 48a, 48b, 49a and 49b to the interior of the blowout preventers 45 and 45a, while being supplied by electric power through transmission cables 50 and 51, respectively. Similar self-contained electrohydraulic operating units may be mounted on the present drilling assembly of FIGURE 1 for supplying pressure fluid to the conduits 52 of the wellhead connector 40 while other operating units (not shown) could be employed to seal and/or lock the landing head 53 to the uppermost blowout preventer 45a, and to operating valves 57 and 58.

Preferably the combined blowout preventers 43, 44, 45 and 45a and the wellhead connector 40 are run together into position on top of the well by being lowered through the water from the drilling platform 11 by means of a pipe string (not shown), commonly known as a running string, with the lower end of the running string being connected to the uppermost blowout preventer 45 by any suitable coupling or connector which may be similar in form to the wellhead connector 40, such as the landing head 53. After the blowout preventers are installed the running string is replaced by a larger diameter pipe string known as a marine conductor pipe which is represented generally in FIGURE 1 by numeral 54.

While the various wellhead components, such for example as the wellhead connector 40 and the blowout preventers 43, 44, 45 and 45a, may be hydraulically, pneumatically or electrically actuatable, they are preferably hydraulically actuatable by means of electro-hydraulic operator units similar to units 46 and 47 although they may be actuated by means of pressure hoses (not shown) which would extend up through the water to the drilling barge 11.

The drilling assembly or stack of blowout preventers 43, 44, 45 and 45a on the top of the wellhead connector is provided with one or preferably two small-diameter conduits which will be termed hereinbelow as choke and kill lines 55 and 56, respectively. The choke and kill lines 55 and 56 are employed to provide means for establishing fluid communication between the drilling platform 11 and the well during drilling operations after one or more of the blowout preventers 4'3, 44, 45 and/or 45a have been closed during an emergency. Thus, the choke line 55 is in communication at its lower end with the interior of the assembly, and hence the well, below the lowermost lblowout preventer 43 While the kill line 56 is in communication with the interior of the assembly below the upper set of blowout preventers 45 and 45a. The choke and kill lines 55 and 56 are provided with remotely actuatable valves 57 and 58, respectively, which have pressure hoses or electrical transmission lines 59 and 60 which extend to the surface or to a valve operator. Since these valves and their connection to the related units do not form an essential part of the present invention and are described in detail in the above-identified copending patent application, they will not be further described here.

As shown in FIGURE 1, the lowermost blowout preventers 43 and 44 are provided with operators 63 and 64, respectively, which are primarily electrically powered 0perators for closing the rams of the blowout preventers. A typical cram-type blowout preventer housing is shown in cross-section in FIGURE 3 as comprising a housing or body member 65 having aligned pipe openings 66 and 67 in one pair of opposite Walls 68 and 69 to provide a passage 70 therethrough for a pipe or tubing member 71. An upper pair of pipe rams 72 and 73 (FIGURE 3) forms the upper ram-type blowout preventer 44 (FIGURE 1). The rams 72 and 73 are slidably mounted in guideways 74 and 75, respectively, and are actuated by linkage arms 76 ap i 77 which are fixedly secured to laterally-extending shafts 7-8 and 79. The terminal adjacent portions of the rams 72 and 73 are provided with sealing elements 80 and 81. When the sealing elements 80 and 81 of the rams 72 and 73 are in sealing engagement, they touch each other on both sides and provide a vertical pipe passage through the sealing elements having a diameter the same as the outside diameter of the pipe 71 against which they would seal.

In a like manner the lower ram-type blowout preventer 43 (FIGURE 1) comprises a pair of laterallymovable rams $2 and 83 mounted in ram guideways 84 and 85, respectively, and movable therein by means of linkage arms 86 and 87 which are fixedly secured to shafts 88 and 89. The lowermost rams 82 and 83, being so called blind rams, are provided m'th sealing elements 90 and 91 having horizontally straight surfaces 92 and 93 which seal against each other along their entire length when the rams 82 and 83 are closed, thereby completely closing the pipe passage 79 through the blowout preventer body member 65.

A typical operator, similar to operator 64 for blowout preventer 44 (FIGURE 1) is shown in FIGURES 4 and 5. The electrical operator comprises a housing 95 (FIGURE 4) having an electric motor 96 mounted therein with an electrical transmission line 97 extending through the wall of the housing 95 in a fiuidtight manner and thence extending up along the drilling assembly to the drilling platform 11 at the surface. The motor 96 is preferably a three-phase motor having its shaft 98 connected by means of a coupling 99 to a drive shaft 100 which has a worm 101 formed thereon. The drive shaft 100 is rotatably mounted in bearings 102 and 103.

The worm 101 meshes with and is arranged to drive a worm gear 194 which is splined to a transverse shaft 105 arranged normal to the drive shaft 100. As shown in FIGURE the transverse drive shaft 105 is mounted in bearings 106, 107, 108 and 109 and has formed thereon worms 110 and 111 of reverse pitch. Worm 110 engages and is adapted to drive the segment worm gear 112 in a clockwise direction at the same time that the worm 111 which engages segment worm gear 113 drives the latter in a counter-clockwise direction. The segment worm gears 112 and 113 would be splined or otherwise fixedly secured for example, say, to the shafts 78 and 79 (FIGURE 3) of the upper rams 80 and 81 so that movement of the segment worm gears 112 and 113 in first one direction and then the other would move the rams toward and then away from the central pipe passage 70 (FIGURE 3).

For emergency service, the electrical operator of the blowout preventer of the present invention is provided with a hydraulic actuator of any suitable type which is adapted to open and close the rams of the blowout preventer when the electric motor 96 of the operator has failed. Thus, as shown in FIGURE 4, a hydraulic motor 115 is also mounted within the operator housing 95 and is provided with pressure conduits 116 and 117 extending therefrom for supplying a pressure fluid to the motor to drive the motor in one direction or the other. A preferred arrangement is to connect the shaft 118 of the hydraulic motor by means of a suitable coupling 119 to the shaft 98 of the electric motor 96. The hydraulic pressure conduits 116 and 1 17 (FIGURE 4) could extend to a power source (not shown) on the deck of the platform 11 (FIGURE 1), or to a secondary-control hydraulic manifold (not shown) but preferably extend to an eleetro-hydraulic operator unit 121 (FIGURE 1) which is similar to the electrohydraulic units 46 and 47 and has an electric transmission cable 122 extending upwardly to a controller 123 on the desk of the barge 11.

The electric motor 96 (FIGURE 4) housed in the electric operator is preferably of a three-phase type having an electric transmission cable 97 running to the controller 123 which is remotely positioned on the deck of the barge 11 (FIGURE 1). The controller 123 is provided with suitable circuits to each of the electric motors positioned on-the wellhead assembly at the ocean floor. One suitable control circuit for an electric motor 96 of the blowout preventer operator is shown in FIGURE as including a variable voltage controller 124 which is electrically connected to the motor 96 through leads 97 and to a power supply 125 through a reversing switch 126. The reversing switch is of any suitable commercial type adapted to reverse the current supply in two of the three leads to the motor 96 so as to run the motor forward or reverse whereby the rams of the blowout preventer may be open or closed. It is desirable to employ a variable voltage controller or variable autotransformer 124 in the circuit so that the closing force of the rams of the blowout preventer may be selectively varied by varying the voltage of the current to the motor 96. One suitable type of a variable autotransformer is one known as Adjust-A-Volt manufactured by Standard Electrical Products of Dayton, Ohio.

It is desirable to be able to adjust selectively the closing force of the rams 72 and 73 (FIGURE 3) on a pipe 71 between the rams and extending through the blowout preventer. This is often necessary because if you close the rams too tightly on the pipe it is impossible to circulate fluid in small amounts past them to prevent buming up the sealing elements and 81 when it is desired to rotate or reciprocate a pipe string in the blowout preventer with the rams closed. On many occasions it is desirable to be able to close the rams of a blowout preventer and then back them off slightly so as to be able to reciprocate the pipe in the rams. During some operations while drilling and completing wells from a floating drilling barge, it is impossible to avoid reciprocating a pipe string as the boat moves up and down. If maximum thrust was applied to the rams to close them on a pipe string passing through the blowout preventer the pipe string may shear off as the wave forces raised the boat at the surface. Thus, it is desirable to provide the blowout preventer of the present invention with a compression-controlling device for the rams of the system.

The amount of thrust exerted by the rams of the blowout preventer may be varied by manually adjusting the variable voltage controller 124 of the circuit. If desired, a current cut-off circuit may be provided in any suitable form as by a pair of current transformers 127 and 128 which are connected to a current-sensitive relay 130 having an adjustable set point device 131 and being connected to a power supply source 132 through a magnetic conta'ctor relay 133 and a circuit breaker 134 in the main power line to the motor 96. A suitable current-sensitive relay 130 may be a continuous Ready Meter Relay type as manufactured by Assembly Products Inc. of Chesterland, Ohio. A time delay relay is also built into the circuit so that the current sensitive relay will ignore inrush current on the starting of the motor 96. With this type of a current cut-0d circuit added to the main voltage controller circuit, when the predetermined thrust has been exerted by the rams against a pipe in the blowout preventer, the current transformers would sense an increase in current and the signal transmitted to the relay 130 would trip the magnetic contactor relay 133 in the power supply line leaving the rams locked against the pipe with the preselected force. If a greater ram closing force were desired, the variable voltage controller would then be changed to increase the voltage output thereof, see FIGURE 11.

While one type of a drive mechanism has been described with regard to FIGURES 4 and 5 which connect the electric motor 96 of the operator to the rams 72 and 73 of FIGURE 3, it is to be understood that many other arrangements may be employed as illustrated in FIG- URES 6 through 9. For example, in FIGURE 6, the shaft 98a of the motor 96a has a worm 10 1a formed thereon which engages a worm gear 135 formed on a transverse shaft, which has reverse pitch worms 137 and 138 formed at opposite ends thereof. The worms 137 and 138 engage worm gear segments 112a and 113a to move the rams 72a and 73a toward and away from each other. In FIGURE 7 individual electric motors 94b and 96b are individually provided to operate the rams 72b and 73b, the shafts of the motor being connected to the shafts of the ram through speed reducers or gear trains 140 and 141.

In FIGURE 8 a single motor 96c is connected through a speed reducer 142 to the end of a shaft 143 having reverse pitch worms 144 and 145 formed thereon. The worms 144 and 145 in turn engage segment worm gears 1120 and 113C to drive shafts 78c and 79c and thus move the arms 72c and 730 toward and away from each other depending upon the direction of which the motor 960 is driven.

In the arrangement shown in FIGURE 9 individual motors 94d and 96d are again employed to drive the individual rams 72d and 73d through speed reducers 146 and 147, worms 148 and 149 of reverse pitch and segment worm gears 112d and 113d, respectively.

Thus, it may be seen that the apparatus of the present invention provides a wellhead positioned below the surface of a body of water and beneath an operating platform positioned above the surface of the water with a large-diameter marine conductor pipe extending from the wellhead to the platform and a plurality of blowout preventers secured to the lower end of the marine conductor pipe and mounted on the wellhead assembly. At least one of the blowout preventers is provided with electricallyor electro-hydraulically actuated operator means mounted adjacent the blowout preventer with power transmission means extending from the operator to the operating platform on the surface of the water. Where circuitmeans are provided for controlling the power supplied to the operator of the blowout preventer, the control circuit preferably having a suitable device for varying the voltage supplied to the operator. The term linkage means as employed in the appended claims is meant to include all of the elements needed to connect operatively the rams 72 and 73 to the motor 76. This would include a motor shaft 98, drive shaft 100, worm 101, worm gear 104, worms 110 and 111, worm gears 112 and 113, shafts 78 and 79 and linkage arms 76 and 77 in the arrangement described with regard to FIGURES 3, 4 and 5.

We claim as our invention:

1. Apparatus for drilling, completing and working over an underwater well from an operating platform positioned above the surface of a body of water, said apparatus comprising:

(a) a wellhead assembly positioned below the surface of the body of water,

(b) an operating platform positioned above the surface of the body of water,

() a large-diameter marine conductor pipe extending from said wellhead assembly up to said operating platform,

(d) a blowout preventer secured in said wellhead assembly and being provided with rams to close about a pipe string,

(e) electrically-actuated operator means operatively connected to said blowout preventer and carried thereby, said operator means including electric motor and linkage means including gear means,

(f) power transmission means extending from said blowout preventer to said operating platform on the surface of the water, said power transmission means including current leads to said electrically-actuated operator means, and

(g) circuit means on said platform connecting said current leads to a power source.

2. Apparatus for drilling, completing and working over an underwater well from an operating platform positioned above the surface of a body of water, said apparatus comprising:

(a) a wellhead assembly positioned below the surface of a body of water,

( 13) an operating platform positioned above the surface of a body of water,

(0) "a large-diameter marine conductor pipe extending from said wellhead assembly up to said operating platform,

(d) a blowout preventer secured in said Wellhead assembly and being provided with rams,

(e) electrically-actuated operator means operatively connected to said blowout preventer and carried thereby, said operator means including electric motor and linkage means including gear means,

(f) power transmission means extending from said blowout preventer to said operating platform on the surface of the water, said power transmission means including current leads to said electrically-actuated operator means,

(g) circuit means on said platform connecting said current leads to a power source, said circuit means including variable voltage means, and

(h) detachable connector means at the lower end of said blowout preventer for connecting it to said wellhead assembly.

3. The apparatus of claim 2 including hydraulicallyoperated motor means carried by said blowout preventer on the outside thereof and being operatively connected to said linkage means thereof for actuating said blowout preventer rams through said linkage means independent of said electric motor means. a

4. Apparatus for drilling, completing and working over an underwater well from an operating platform positioned above the surface of a body of water, said apparatus comprising:

(a) a wellhead assembly positioned below the surface of a body of water,

(b) an operating platform positioned above the surface of the body of water,

(c) a large-diameter marine conductor pipe extending from said Wellhead assembly up to said operating platform,

(d) a plurality of blowout preventers secured together in axial arrangement, the upper end of said uppermost preventer being secured to the lower end of said marine conductor pipe, at least one of said blowout preventers being provided with rams,

(e) electrically-actuated operator means operatively connected to the rams of at least one of said blowout preventers and carried thereby, said operator means including electric motor and linkage means including gear means,

(f) power transmission means extending from said blowout preventers to said operating platform on the surface of the water, said power transmission means including current leads to said electricallyactuated operator means,

(g) circuit means on said platform connecting said current leads to a power source, said circuit means including manually operable variable voltage means, and

(h) detachable connector means at the lower end of said lowermost blowout preventer for connecting it to said wellhead assembly.

References Cited by the Examiner UNITED STATES PATENTS 887,253 5/1908 Jackson 251- 1,529,005 3/ 1925 Beckwith 251-135 X 1,875,673 9/1932 Stockstill 251-1 X 2,846,178 8/1958 Minor 251-1 2,947,508 8/ 1960 Allen 251-1 3,012,610 12/1961 Bauer et a]. 166-665 3,032,125 5/1962 His r et a1. -7 3,052,299 9/ 1962 Geer et a1. 166-665 3,064,735 11/ 1962 Bauer et a1. 166-665 3,071,188 1/1963 Raulins 166-665 3,142,337 7/1964 Poorman 'et a1 166-665 3,147,992 9/1964 Haeber et 'al. 166-665 X CHARLES E. OCONNELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner. 

1. APPARATUS FOR DRILLING, COMPLETING AND WORKING OVER AN UNDERWATER WELL FROM AN OPERATING PLATFORM POSITIONED ABOVE THE SURFACE OF A BODY OF WATER, SAID APPARATUS COMPRISING: (A) A WELLHEAD ASSEMBLY POSITIONED BELOW THE SURFACE OF THE BODY OF WATER, (B) AN OPERATING PALTFORM POSITIONED ABOVE THE SURFACE OF THE BODY OF WATER, (C) A LARGE-DIAMETER MARINE CONDUCTOR PIPE EXTENDING FROM SAID WELLHEAD ASSEMBLY UP TO SAID OPERATING PLATFORM, (D) A BLOWOUT PREVENTER SECURED IN SAID WELLHEAD ASSEMBLY AND BEING PROVIDED WITH RAMS TO CLOSE ABOUT A PIPE STRING, (E) ELECTRICALLY-ACTUATED OPERATOR MEANS OPERATIVELY CONNECTED TO SAID BLOWOUT PREVENTER AND CARRIED THEREBY, SAID OPERATOR MEANS INCLUDING ELECTRIC MOTOR AND LINKAGE MEANS INCLUDING GEAR MEANS, (F) POWER TRANSMISSION MEANS EXTENDING FROM SAID BLOWOUT PREVENTER TO SAID OPERATING PLATFORM ON THE SURFACE OF THE WATER, SAID POWER TRANSMISSION MEANS INCLUDING CURRENT LEADS TO SAID ELECTRICALLY-ACTUATED OPERATOR MEANS, AND (G) CIRCUIT MEANS ON SAID PLATFORM CONNECTING SAID CURRENT LEADS TO A POWER SOURCE. 